Wireless inductive power transfer

1. A power transmitter for transferring power to a power receiver during a power transfer phase using a wireless inductive power signal, the power transmitter comprising: an inductor that provides the power signal; a power signal generator configured to drive the inductor to provide the power signal; a message receiver that receives data messages from the power receiver, wherein the data messages are communicated by load modulation of the power signal; wherein the data messages include at least a power control message and a query message; a power loop controller, wherein the power loop controller operates in at least two modes; wherein, in a first mode: if a value of the power control message is a first value, the power loop controller increases a magnitude of the power signal; and if a value of the power control message is a second value, the power loop controller decreases the magnitude of the power signal; wherein, in a second mode: if a value of the power control message is the first value, the power loop controller does not increase the magnitude of the power signal; and if a value of the power control message is the second value, the power loop controller does not decrease the magnitude of the power signal; wherein the power loop controller normally operates in the first mode; and a modification processor circuit, wherein, in response to a received query message, the modification processor circuit causes the power loop controller to temporarily enter the second mode; wherein, in the second mode: the power loop controller modifies the power signal in accordance with a first pattern of modifications provided by the modification processor circuit; and wherein the modification processor circuit selects the first pattern from a plurality of patterns of modifications in response to the query message, each pattern of the plurality of patterns corresponding to a different response to the query message.

2. The power transmitter of claim 1 , wherein the query message comprises an indication of a desired modification of the magnitude of the power signal in the second mode.

3. The power transmitter of claim 1 , wherein the power loop controller modifies the magnitude of the power signal by changing an inductor current.

4. The power transmitter of claim 1 , wherein the query message comprises a device identification, and the power loop controller modifies the magnitude of the power signal based on the device identification.

5. The power transmitter of claim 1 , wherein the query message comprises an indication of a technical specification with which the power receiver complies, and, in the second mode, the power loop controller modifies the magnitude of the power signal based on the indication of the technical specification.

6. The power transmitter of claim 1 , wherein the query message is included in a configuration message transmitted prior to initialization of a power transfer phase.

7. The power transmitter of claim 1 , wherein the power loop controller modifies the power signal based on a capability of the power transmitter.

8. A power transfer system comprising the power transmitter according to claim 1 .

9. The method of claim 1 , wherein the query message comprises a device identification, and the power loop controller modifies the magnitude of the power signal based on the device identification.